This invention relates generally to heat exchange coils or evaporators and, more specifically, to heat exchange coils for use in connection with systems for cooling or freezing food products. Such heat exchange coils are a normal component of any mechanical refrigeration system in which a refrigerant is compressed and cooled in a condenser to liquify the refrigerant. The liquified and cooled refrigerant is then circulated through an expansion valve to an evaporator including the heat exchange coil where heat absorption by the refrigerant takes place. The refrigerant passes through the tubes or coils of the heat exchanger absorbing heat from air circulated between the tubes or coils.
Much of the apparatus used in connection with freezing various types of meat, chicken and fish, utilize mechanical refrigeration apparatus. Such refrigeration apparatus involves the cooling of air which is repeatedly recirculated through heat exchange coils. These coils typically include a large number of closely spaced sections of tubing through which a refrigerant is circulated. The air which is to freeze the food products is cooled by passing it into contact with exterior surfaces of the tubing and fins which are attached to the tubing to increase the effective heat transfer between the air and the refrigerant.
In connection with the preparation and freezing of such food products, it is extremely important that all possible steps be taken to maintain sanitary conditions within the food processing plant. There are many toxic types of bacteria which have been found to be present and thrive in such food processing plants. When problems develop with the output of such food processing plants being contaminated with such bacteria, it is often difficult to locate the source of such contamination. There are types of bacteria that may be transported in the circulating air and which may deposit and grow in various apparatus associated with the processing of such foods. In this connection it has been determined that in some instances bacteria have been deposited in the evaporator coils associated with the refrigeration apparatus for freezing such food products.
The risk of bacterial contamination in food freezing plants is particularly high in processing plants for freezing chickens. Such plants typically process a large volume of chickens which are slaughtered, dressed and frozen on a continuous processing line. The close proximity of the various steps in the processing and the difficulty in maintaining sanitary conditions during the very rapid processing of the chickens through these steps results in a high risk of such bacterial contamination of the product and the equipment used in the processing. As a consequence there is a need for food processing or food freezing equipment that is specifically designed to facilitate simple and effective cleaning to eliminate sources of bacterial food contamination.
In the conventional form of the evaporator or heat exchange coils used in refrigeration systems for freezing food products, there are many heat exchange tubes and interconnecting heat transfer fins and plates which are distributed throughout a fairly elongated passageway through which the air to be cooled passes. Because of the close proximity of the tubes and the heat transfer plates to each other, it is almost impossible to get sufficient access to the interior portions of the heat exchanger to enable one to clean and sanitize all of the areas through which the air to be cooled passes.
There are currently no evaporators on the market which include practical and effective means for cleaning and sanitizing the evaporator coils of equipment used in the fast freezing of food products such as chicken. There are patents relating to the removal of frost or ice from refrigeration heat exchange coils. U.S. Pat. Nos. 3,828,570 to Stutz teaches the spraying of an anti-freeze liquid onto the heat exchange tubes, to remove ice therefrom. The U.S. Pat. No. 2,097,851 to Wenzl discloses the use of a water spray to remove frost from heat exchange cooling coils. The use of heated air for defrosting heat exchange coils in an evaporator is shown in the U.S. patents to Shrader, U.S. Pat. No. 2,130,036 and to Ballarin et al. U.S. Pat. No. 4,006,601. U.S. Pat. Nos. 4,528,820 and 4,570,447 to Jonassen teach the use of compressed air to remove frost from heat exchange tubes. U.S. Pat. No. 1,978,555 to Snow which relates to a heat exchanger associated with a gas-fired heater, teaches the use of water spray means to clean soot off the heat exchange tubes therein.